feat(ui): 增加关于弹窗（PineSound 品牌）

- AboutDialog：品牌 Logo/产品名/版本/技术栈/版权，Esc 或点击遮罩关闭
- PageHeader 右上角新增「ⓘ 关于 PineSound」入口（info 图标）
- 样式：about-* 系列（毛玻璃遮罩 + 渐变品牌块），跟随 DPM 配色

src/styles/datascreen.css

@@ -2554,3 +2554,134 @@
 @media (max-width: 1280px) {
   .bd-hd-media-name { display: none; }
 }
+
+/* ==================== 关于 PineSound 弹窗 ==================== */
+.bd-about-btn {
+  flex: none;
+  width: 30px;
+  height: 30px;
+  border-radius: 50%;
+  border: 1px solid rgba(47, 107, 255, 0.25);
+  background: rgba(255, 255, 255, 0.7);
+  color: var(--bd-sub, #7d8fa9);
+  display: inline-flex;
+  align-items: center;
+  justify-content: center;
+  cursor: pointer;
+  transition: all 0.2s;
+}
+.bd-about-btn:hover {
+  color: #2f6bff;
+  border-color: #2f6bff;
+  background: #fff;
+}
+
+.about-overlay {
+  position: fixed;
+  inset: 0;
+  z-index: 300;
+  background: rgba(13, 28, 48, 0.45);
+  backdrop-filter: blur(4px);
+  -webkit-backdrop-filter: blur(4px);
+  display: flex;
+  align-items: center;
+  justify-content: center;
+}
+.about-modal {
+  position: relative;
+  width: min(420px, calc(100vw - 48px));
+  background: #fff;
+  border-radius: 16px;
+  padding: 28px 30px 22px;
+  box-shadow: 0 24px 60px rgba(15, 42, 96, 0.28);
+  animation: about-pop 0.25s ease;
+}
+@keyframes about-pop {
+  from { opacity: 0; transform: translateY(12px) scale(0.97); }
+  to   { opacity: 1; transform: none; }
+}
+.about-close {
+  position: absolute;
+  top: 12px;
+  right: 14px;
+  width: 28px;
+  height: 28px;
+  border: none;
+  background: transparent;
+  color: #9fb0c6;
+  font-size: 20px;
+  line-height: 1;
+  cursor: pointer;
+  border-radius: 8px;
+}
+.about-close:hover { color: #1d2c44; background: #f0f4fa; }
+
+.about-brand { text-align: center; margin-bottom: 6px; }
+.about-logo {
+  width: 64px;
+  height: 64px;
+  margin: 0 auto 10px;
+  border-radius: 18px;
+  background: linear-gradient(135deg, #2f6bff 0%, #22d3ee 100%);
+  color: #fff;
+  font-size: 26px;
+  font-weight: 800;
+  letter-spacing: 0.02em;
+  display: flex;
+  align-items: center;
+  justify-content: center;
+  box-shadow: 0 10px 24px rgba(47, 107, 255, 0.35);
+}
+.about-name {
+  margin: 0;
+  font-size: 24px;
+  font-weight: 800;
+  color: #1d2c44;
+  letter-spacing: 0.04em;
+}
+.about-product {
+  margin-top: 4px;
+  font-size: 13px;
+  color: #7d8fa9;
+}
+.about-tagline {
+  text-align: center;
+  margin: 14px 0 18px;
+  font-size: 12.5px;
+  color: #4a5b74;
+  line-height: 1.6;
+  padding: 10px 12px;
+  background: #f5f8ff;
+  border-radius: 10px;
+}
+.about-section h4 {
+  margin: 0 0 8px;
+  font-size: 12px;
+  color: #7d8fa9;
+  letter-spacing: 0.08em;
+}
+.about-section ul {
+  margin: 0;
+  padding: 0;
+  list-style: none;
+  display: flex;
+  flex-direction: column;
+  gap: 6px;
+}
+.about-section li {
+  font-size: 12.5px;
+  color: #33425c;
+  padding: 6px 10px;
+  background: #f8fafd;
+  border-radius: 8px;
+  border: 1px solid #eef2f8;
+}
+.about-meta {
+  margin-top: 18px;
+  padding-top: 14px;
+  border-top: 1px dashed #e3ecf7;
+  display: flex;
+  justify-content: space-between;
+  font-size: 11px;
+  color: #9fb0c6;
+}